For example, a photo printer records an image by so-called scanning exposure that scans recording light in a main scan direction perpendicular to a sub scan direction while nipping and conveying a cut-sheet of photosensitive material in the sub scan direction by plural pairs of conveyer rollers provided on a paper path.
In order to obtain a high-quality photo print, it is necessary that the photosensitive material is exposed in an appropriate position and direction. However the cut-sheet of photosensitive material often skews during being conveyed because of mounting tolerance of units in the photo printer and tolerance of parts of individual units. When the photosensitive material on the skew is exposed, the recorded image is also on the skew to the photosensitive material. Especially because the photo print is often output as a white-rimmed print where the recorded image is surrounded with a white rim of a given width, the image recorded on the skew extremely degrades the quality of the photo print.
The skew can be corrected by striking a leading edge of an individual sheet of photosensitive material on a conveyer roller pair in its stopping state and by squeezing the sheet in between the conveyer rollers of the pair till the whole leading edge is oriented parallel to an axial direction of the conveyer rollers, i.e. a main scan direction, while bending the photosensitive material flexibly and sufficiently enough to correct the skew.
As disclosed in Japanese Laid-open Patent Application No. 2001-174927, especially in pages 5 and 6, in order to improve a processing capacity of the photo printer (the number of processed sheets per unit time), it is preferable to record images simultaneously on plural sheets of photosensitive material which are apposed in the main scan direction and are conveyed in parallel to each other along the sub scan direction. In this case, the skew can also be corrected by striking the leading edges of the plural sheets on a conveyer roller pair in its stopping state and by flexibly bending the sheets of recording material. In addition to that, this method is useful for aligning the leading edges of the apposed sheets as well as for correcting the skew.
As the sheets of photosensitive material conveyed in plural lines are different in skew degree or in leading edge position between the lines, transport amounts or squeezing amounts necessary for correcting the skew of the respective sheets are different between the lines. In order to correct the skew of any sheet without fail, it is necessary to preset the transport amount so large that it takes more time to correct the skew. As a result, the processing capacity per unit time goes down.